Ok, I just updated the "test" post using your suggestion, language = "text" Then, I deleted the photo I had in there. I inserted a photo from the media gallery - the recommended photos. After the first photo, there was no change in the source code section - the regular expression looked correct. Then, I inserted a second photo, and that is when the bad replacements started happening. When I inserted a third photo, every ampersand was replaced by &, so it just sort of devolved from there.
I'm not sure what would happen if I just inserted a photo from the media library, rather than the media gallery. I have a hunch I could get around this by inserting the image, copying to my desktop, saving to my media library and inserting from there, but that is really a convoluted workaround. I haven't tried that, but my hunch is that because the recommendation engine must be parsing my text, there is a lot of interaction with the text and code that wouldn't happen if I just inserted from media gallery, but you'll know better than I will.